package encrypt;
import Config.setting;
import java.security.SecureRandom;

import javax.crypto.Cipher;
import javax.crypto.KeyGenerator;
import javax.crypto.SecretKey;
import javax.crypto.spec.SecretKeySpec;
 /**
  * 
  * @author thanhnx
  * encode, decode data by secret key.
  */
public class AesCrypto {
	private static String secret = setting.encryptKey;
 
	public String encrypt(String original) {
		byte[] rawKey;
		byte[] result;
		try {
			rawKey = getRawKey();
			result = encrypt(rawKey, original.getBytes());
		} catch (Exception e) {
			return "";
		}
		return toHex(result);
	}
 
	public String decrypt(String encrypted) {
		byte[] rawKey;
		byte[] enc;
		byte[] result;
		try {
			rawKey = getRawKey();
			enc = toByte(encrypted);
			result = decrypt(rawKey, enc);
		} catch (Exception e) {
			result = new byte[0];
			e.printStackTrace();
		}
        return new String(result);
	}
 
	private static byte[] getRawKey() throws Exception {
		KeyGenerator kgen = KeyGenerator.getInstance("AES");
		SecureRandom sr = SecureRandom.getInstance("SHA1PRNG");
		sr.setSeed(secret.getBytes());
		kgen.init(128, sr); // 192 and 256 bits may not be available
		SecretKey skey = kgen.generateKey();
		byte[] raw = skey.getEncoded();
		return raw;
	}
 
	private static byte[] encrypt(byte[] raw, byte[] clear) throws Exception {
		SecretKeySpec skeySpec = new SecretKeySpec(raw, "AES");
		Cipher cipher = Cipher.getInstance("AES");
		cipher.init(Cipher.ENCRYPT_MODE, skeySpec);
		byte[] encrypted = cipher.doFinal(clear);
		return encrypted;
	}
 
	private static byte[] decrypt(byte[] raw, byte[] encrypted) throws Exception {
		SecretKeySpec skeySpec = new SecretKeySpec(raw, "AES");
		Cipher cipher = Cipher.getInstance("AES");
		cipher.init(Cipher.DECRYPT_MODE, skeySpec);
		byte[] decrypted = cipher.doFinal(encrypted);
		return decrypted;
	}
 
	public static String toHex(String txt) {
		return toHex(txt.getBytes());
	}
 
	public static String fromHex(String hex) {
		return new String(toByte(hex));
	}
 
	public static byte[] toByte(String hexString) {
		int len = hexString.length() / 2;
		byte[] result = new byte[len];
		for (int i = 0; i < len; i++)
			result[i] = Integer.valueOf(hexString.substring(2 * i, 2 * i + 2), 16).byteValue();
		return result;
	}
 
	public static String toHex(byte[] buf) {
		if (buf == null)
			return "";
		StringBuffer result = new StringBuffer(2 * buf.length);
		for (int i = 0; i < buf.length; i++) {
			appendHex(result, buf[i]);
		}
		return result.toString();
	}
 
	private final static String HEX = "0123456789ABCDEF";
 
	private static void appendHex(StringBuffer sb, byte b) {
		sb.append(HEX.charAt((b >> 4) & 0x0f)).append(HEX.charAt(b & 0x0f));
	}
}